There are 13 essential vitamins, which are classified into two groups: water-soluble vitamins (vitamin C and B-complex vitamins) and fat-soluble vitamins (vitamins A, D, E, and K).

When the body lacks essential vitamins, it can lead to various health problems. 

Some of the most common consequences of vitamin deficiency are:

Weak immune system: Vitamin C and vitamin D are essential for the proper functioning of the immune system. Lack of these vitamins can weaken it, making us more susceptible to infections and diseases.

Anemia: Iron and vitamin B12 are essential for the formation of red blood cells. A lack of these vitamins can cause anemia, a condition in which the body does not have enough red blood cells to carry oxygen to the tissues.

Poor bone health: Vitamin D and calcium are essential for the development and maintenance of strong bones. Their deficiency can lead to osteoporosis, a condition in which bones become weak and brittle.

Vision problems: Vitamin A is essential for good vision. Its absence can lead to vision problems.

Skin problems: Vitamin E is important for healthy and glowing skin.

Nerve damage: Vitamin B12 and other B-complex vitamins are essential for the proper functioning of the nervous system. A deficiency of these vitamins can cause nerve damage, leading to numbness, tingling and other symptoms.

Delayed wound healing: Vitamin C is essential for the formation of collagen, a protein that is important for wound healing. 

Muscle weakness: Potassium and magnesium are essential for proper muscle function. 

Fatigue and weakness: Vitamins B1, B2, B3 and B6 are important for the production of energy in the body. Lack of these vitamins can cause fatigue, weakness and other symptoms.

People can't get all the nutrients they need from their diet, not only because of their diet, but also because of their lifestyle in general. Therefore, we often turn to supplements to fill these nutritional "gaps".